The invention relates to an electrochemical energy storage cell, in particular to an energy store in a vehicle electrical system.
The automobile sector is increasingly using electrochemical energy stores, constructed of individual cells, preferably energy stores, constructed of double layer capacitors. When energy is stored and made available for use, these double layer capacitors offer the advantage that they may provide high performance for a short period of time. To arrive at the supply voltage required in a motor vehicle, the individual energy storage cells are connected in series. The technical aspects of double layer capacitors, such as their construction and manufacture, are comparable to those of batteries, especially lithium ion batteries. The materials that are used are similar to some extent. It involves predominantly monopolar arrangements, in which the electrodes are wound or stacked.
As a rule, the liquid electrolyte decomposes over the lifetime of the energy storage cells; and gaseous decomposition products are generated. This applies especially under the additional influence of higher temperatures, as is the case in motor vehicles. As a rule, the decomposition products are collected in the energy storage cell or an arrangement of several energy storage cells and vented to the atmosphere via a venting hose. Such a device has already been disclosed in DE 101 28 672 A1. Owing to the tolerances of the cells, the cell voltages diverge in the course of cyclic charging and discharging. This is critical, above all, when the maximum cell voltage is reached. The consequences extend from differential ageing of the cells up to the failure of individual cells. Furthermore, series-connected electrochemical energy storage cells exhibit a non-uniform distribution of voltage over the individual cells owing to the different internal resistances and/or the different capacities of the individual cells. Electronic circuits may be used to avoid overvoltages when charging and discharging. Such electronic circuits range from simple compensating resistors to totally active circuits, which are provided, as a rule, once per cell and once in an overreaching manner for a cell arrangement.
Both the electrical connection of the individual electrochemical energy storage cells and their respective monitoring logic, as well as the collection of the gaseous decomposition products and their venting into the atmosphere, represent a problem when a large number of electrochemical energy storage cells are wired together.
Therefore, the object of the invention is to provide an alternative construction of an electrochemical energy storage cell, which makes possible both a simple electrical connection as well as a simple venting of the resulting gaseous decomposition products in series-connected electrochemical energy storage cells.
The invention solves this problem by means of an electrochemical energy storage cell that exhibits a core tube, which passes through the energy storage cell and is open on its two ends.
As a consequence, the invention offers the possibility of integrating into the core tube not only one or more connections for supplying or dissipating energy and a databus structure for linking the individual cells together in an intelligent manner, but also provides a channel for siphoning off any electrolytes that may have become liberated. The result is that a simple cascading/series connection of the individual cells is possible.
Advantageous further developments and embodiments of the invention are described and claimed herein.
Preferably, the core tube forms a connection lead of the energy storage cell. In this case, the supply/dissipation of electric power and/or the databus structure may be realized by means of merely one additional lead to the core tube. To this end, the electrochemical energy storage cell exhibits preferably a conducting exterior housing, which is electrically insulated at least against the core tube, and/or at least one lead, which is arranged in the core tube and which also includes preferably at least one connection lead of the energy storage cell.
In the electrochemical energy storage cell, according to the invention, the core tube and/or at least one lead, arranged in the core tube, comprise/comprises at least one lead of a databus. The databus may also be integrated in the connection lead for supplying and dissipating energy.
The inventive electrochemical energy storage cell, which exhibits at least one lead, arranged in the core tube, includes preferably at least one guide element for the at least one lead, which is arranged in the core tube and by which the core tube is not closed. In this case, the electrochemical energy storage cell, according to the invention, may be cooled with air or liquid via the core tube. Furthermore, it is also possible to siphon off any electrolytes, which might have become liberated, through the core tube.
Preferably, the electrochemical energy storage cell, according to the invention, exhibits an electronic circuit for controlling, regulating and/or monitoring the energy storage cell. Owing to such an electronic circuit, which is also preferably an electronic slave, controlled by an electronic master, both the overvoltages and a diverging of the cell voltages during cyclic charging and discharging may be avoided. Furthermore, the consequence of such an electronic circuit is a temperature monitoring of the cell, the core tube and/or the channel, which is formed by said core tube; a voltage monitoring of the cell and/or the connection leads; and/or a current monitoring of the cell. Furthermore, it is also possible that the result of such an electronic circuit is a pressure monitoring of the cell and/or the core tube; a measurement of the throughflow of gas or a gas mixture, present in the core tube; and/or a monitoring of the occurrence of a (specific) gas or gas mixture, present in the core tube.
The electrochemical energy storage cell, according to the invention, exhibits preferably at least one overpressure valve, leading into the core tube. The consequence of this overpressure valve is that gaseous decomposition products of the electrochemical energy storage cell may be conveyed specifically into the core tube and vented safely and simply into the atmosphere. Furthermore, this venting into the atmosphere is done preferably by way of an activated charcoal filter and/or a molecular sieve for trapping at least a fraction of the decomposition products.
The inventive electrochemical energy storage cell exhibits preferably at least one cooling rib, arranged in the core tube. In the event that the inventive energy storage cell also exhibits a guide element for the at least one lead, arranged in the core tube, the at least one cooling rib is also formed in an integrated manner preferably with the guide element. The result of the at least one cooling rib, arranged in the core tube, is that the core tube may also be subdivided into a plurality of channels that may have different functions, for example, a channel for venting gaseous decomposition products of the energy storage cell, a channel for cooling the fluid, a channel for guiding the electrical lines, etc.
The electrochemical energy storage cell, according to the invention, includes preferably at least one sensor for measuring a cell temperature, a temperature in the core tube, a cell voltage, a voltage of the connection lead of the cell, a current taken from the cell, a pressure in the cell, a pressure in the core tube, a throughflow of a gas or a gas mixture present in the core tube, and/or a chemical composition or the occurrence of a (specific) gas or gas mixture present in the core tube.
The inventive energy storage cell is preferably an accumulator or a double layer capacitor.
Other details, advantages and features of the present invention are disclosed in the following description of the embodiments with reference to the drawings.